Preterm birth is not only the major cause of infant mortality, but also places the surviving individual at increased risk for significant mental and physical disabilities and major adult diseases. The preterm premature rupture of the fetal membranes (PPROM) is the cause of 30-40% of all preterm births and about 40% of these are due to infection. We have identified the only non-infectious pathway for PPROM to date. In these women with PPROM and no infection, there is increased expression of the relaxin genes and proteins in the decidua and placenta. Relaxin causes increased growth of the fetal membranes via stimulation of IGF-ll and increased degradation of the extracellular matrix (ECM). We have measured 488 genes in rare PPROM tissues, devoid of many of the usual confounding variables associated with preterm birth and shown relaxin and the expression of 29 other genes altered. From these data, three sets of genes/gene pathways have been chosen for further study: a pathway for development/growth, an inflammatory pathway and two genes whose products alter the structure of the ECM. We will place relaxin into the context of these changes, in order to understand this pathology further. Thus, in Specific Aim 1, we will study the relationships of relaxin to the genes/pathways altered at PPROM, in cell lines, tissue explants and in vivo. In Specific Aim 2, we will carry out a collaborative study using a rhesus monkey model and give relaxin directly into the amniotic cavity at preterm. The structure of the membranes and the genes/pathways of interest will be studied. In Specific Aim 3, an in vitro model will be used to study the effects of the rupture on the tissue. This will allow us to distinguish the cause of PPROM from its effect. These changes will then be sought after PPROM in vivo. The combined results will significantly increase our understanding of the non-infectious cause(s) of PPROM.